This invention relates to improvements in a system for integrally controlling an automatic transmission and an engine.
Automatic transmissions are known to include gear transmission mechanisms, a plurality of frictionally engaging devices, and hydraulic pressure control devices operated to selectively switch the engagements of the frictionally engaging devices, so that any one of plurality of gear stages can be achieved in accordance with a preset shift map.
Furthermore, in an automatic transmission for a vehicle of the type described, various systems are known for integrally controlling an automatic transmission and an engine, wherein engine torque is changed during shifting to obtain satisfactory shift characteristics and durability of the frictionally engaging devices. More specifically, the system for integrally controlling the automatic transmission and the engine of the type described changes the amount of torque transmitted from the engine during shifting and controls the amount of energy absorbed in various members of the automatic transmission or in the frictionally engaging devices so as to complete a shifting within a short period of time under a low shift shock, whereby a satisfactory shift feeling is given to a driver and durability of the frictionally engaging devices is improved.
Now, in constructing the above-described system, when means for controlling the engine, means for controlling the automatic transmission and further control means for determining processing data including the engine torque change timing and engine torque change value are integrally provided in the system, increased capacity of a computer leads to increased cost. In addition it is disadvantageous to mount the system on a vehicle which has a high limitation in storage space.
Furthermore, adoption of the integrally controlling system may be disadvantageous from the viewpoints of all-around properties or common-purpose properties of the aforesaid control means, because there are vehicles which require no engine torque control.
To obviate the above-described disadvantages, there has been proposed a technique wherein the aforesaid control means are provided separately of each other.
However, when the means for controlling the engine and the means for controlling the automatic transmission are formed separately of each other as described above, in order to change the engine torque during shifting, it becomes necessary to provide various inevitable communication means for connecting both control means to each other. Furthermore, the communication means may cause a problem in that these communication means may be disconnected or short-circuited. As a result, an engine torque change control cannot be adequately carried out when the engine torque change control should properly be performed. If the aforesaid situation occurs, then an energy value absorbed in the frictionally engaging devices increases, whereby the durability of these frictionally engaging devices is deteriorated. Furthermore, such a problem also occurs that the shift duration is prolonged, whereby the shifting is not completed within a shockless region of an accumulator, so that shift shocks become high. This is because, on the automatic transmission side, shift tuning data such as oil pressure are preset in expectation of decreasing the engine torque by a predetermined value during the shifting.